Traditionally, molecular studies of population structure, diversity, end dynamics have relied on allozymes end mitochondrial DNA. This is generally due to the technical difficulty involved in studying the primary genetic material directly. In recent years, technical advances have made direct examination of nuclear DNA feasible, and it is now practical to go directly to the source of genetic diversity and activity in populations. My students and l began developing this capability about two years ago, as the technologies associated with the polymerase chain reaction, DNA fingerprinting, non-radioactive DNA detection, and RFLP analysis were created and improved. We have spent the past two years developing the ability to perform nuclear DNA-based population studies using these new technologies. We have done pilot studies on several fish species and find nuclear polymorphisms in every species studied. In the course of these studies, we have improved techniques to the point that informative probe.enzyme combinations can be found readily. The non-radioactive detection system we use is sensitive enough to detect single copy DNA sequences, and probes that are known to be informative can be stored and reused for long periods. Application of the polymerase chain reaction increases efficiency even more by eliminating the need to produce probes by bacterial cloning. We have had to depend on people in other labs and institutions for the fish used in these studies, and we have been hampered in our attempts to do an effective population study. The study proposed here is exciting because we will do our own collecting and use the organisms we collect to examine many different aspects of population biology simultaneously -- effects of a bottleneck on population diversity, accumulation of genetic differences between populations that have been separated for long periods, and the dynamics of structure and gene flow within a population that extends over an extensive range. Moreover, simultaneous measurements can be made using two systems --- mitochondrial and nuclear -- that will help identify the relative limitations and advantages of each technique. The methods to be employed in this study are so fundamental that experience gained by the MBRS students who will be involved will be applicable to most other areas that involve biotechnology, including medicine, agriculture, pharmacology, and basic biology. Judging from the success students in my lab have had in going on to more advanced institutions of their choice, study and application of the techniques we are using seems to be an effective springboard to further training.